Changes in the Fecal Flora of Patients with Crohn's Disease During Treatment with Metronidazole

Abstract

Six patients with Crohn's disease and three healthy volunteers were treated with metronidazole. Before and during metronidazole treatment quantitative and qualitative studies of the aerobic and anaerobic fecal bacterial flora were performed, and the minimal inhibitory concentration (MIC) values for metronidazole of the isolated bacteria were determined. There was no significant change in the fecal flora of the volunteers during metronidazole treatment, but three patients who clinically responded well to treatment had drastically changed their anaerobic flora. Two patients did not respond to the metronidazole therapy. The total anaerobic count for one of them was unchanged, and the number of isolated anaerobic species was high during the treatment. The total anaerobic counts of the other non-responder decreased, but metronidazole-resistant (MIC greater than or equal to 40 microgram/ml) Gram-negative rods remained in the fecal samples. Furthermore, after 2 months his condition worsened, and he was given corticosteroids and parenteral nutrition. The result in one patient with a moderate response to therapy was intermediate. Our observations may explain why some patients benefit from metronidazole therapy and others do not.